This invention relates to a system adopted for recognizing broadcast information. More particularly, this invention relates to a method and apparatus for determining whether an item of broadcast information corresponds to any of a plurality of items of information previously stored in a reference library.
A wide variety of copyrighted recordings and commercial messages are transmitted by broadcast stations. Copyrighted works such as moving pictures, television programs, and phonographic recordings attract audiences for broadcast stations, and the aforementioned commercial messages, when sent to the audiences, provide revenue for the broadcast stations.
There is an interest among various unions, guilds, performance rights societies, copyright owners, and advertising communities in knowing the type and frequency of information being broadcast. Owners of copyrighted works, for example, may be paid a royalty rate by broadcast stations depending on how often their copyrighted work is broadcast. Similarly, commercial message owners who pay broadcast stations for air time have an interest in knowing how often their commercial messages are broadcast.
It is known in the art that commercial radio and television broadcast stations are regularly monitored to determine the number of times certain information is broadcast. Various monitoring systems have been proposed in the prior art. In manual systems, which entail either real-time listening or delayed listening via video or audio tapes, people are hired to listen to broadcast information and report on the information they hear. Manual systems although simple, are expensive, unreliable, and highly inaccurate.
Electronic monitoring methodologies offer advantages over manual systems such as lower operating costs and reliability. One type of electronic monitoring methodology requires insertion of specific codes into broadcast information before the information is transmitted. The electronic monitoring system can then recognize a song, for example, by matching the received code with a code in a reference library. Such systems suffer from both technical and legal difficulties. For example, such a coding technique requires circuitry, which is expensive to design and assemble and which must be placed at each transmitting and receiving station. Legal difficulties stem from the adverse position of government regulatory agencies toward the alteration of broadcast signals without widespread acceptance thereof by those in the broadcast industry.
A second type of electronic monitoring methodology requires pre-specification of broadcast information into a reference library of the electronic monitoring system before the information can be recognized. A variety of pre-specification methodologies have been proposed in the prior art. The methodologies vary in speed, complexity, and accuracy. Methodologies which provide accuracy are likely to be slow and complex, and methodologies which provide speed are likely to be inaccurate.
Regarding accuracy, for example, there exists a time-bandwidth problem with electronic monitoring systems which divide the received broadcast information into nonoverlapping time segments and perform Fourier or analogous transforms on each segment to arrive at a description of the received broadcast information in frequency space. If the time segments are made long to achieve good resolution of the low frequency components of the broadcast information, the resulting system looses its ability to recognize broadcast information played at a slightly different speed than that used to record the information into the electronic monitoring system reference library. Conversely, if the time segments are made too short in an effort to minimize the above-mentioned deficiency, the information contained in the resulting frequency data is not unique enough to allow the system to distinguish between similar sounds, and hence recognition errors result.
Another problem in the prior art of electronic monitoring is that electronic monitoring systems require advance knowledge of broadcast information. Electronic monitoring systems which rely on the pre-specification of broadcast information are unable to recognize broadcast information not in the electronic monitoring system's reference library. As a consequence, broadcast information is not recognized, and the necessity to enroll unspecified broadcast information into the electronic monitoring system reference library creates a bottleneck that may effectively decrease the accuracy and efficiency of the electronic monitoring system. Thus, in view of the above problems, there exists a need in the electronic monitoring art to develop a broadcast information monitoring system which is both efficient and accurate.